Niagara Toilets are fairly simple to diagnose and repair. If your Niagara toilet is running, you will need to check to see if the flapper is leaking, or the fill-valve is over-flowing, or the if the flush valve has a leak. Leaky, running Niagara toilets can waste a fortune in water waste, if left unattended for too long.

If the Niagara toilet is leaking from the bolts, or the gasket or seal, then you know the nuts and bolts that hold the tank to the bowl are likely corroded and the rubber has turned black and deteriorated on the gaskets.
Troubleshooting a sticky handle, a runny toilet, or a leak in the Niagara toilet is simply a matter of using the Niagara Toilet Diagnostic Chart below.

If you notice the toilet making a noise or the Niagara rubber flapper seal or float is deteriorating and leaking, then you can easily change it by buying a new flapper or repairing the flush valve mechanism, and tank disc or ball. If the Niagara toilet uses a tank ball, you can replace it by threading the brass stem into the new tank ball clockwise and testing it out to make sure that the water is not leaking out, and no drips or runs are happening.

If the toilet is pressure-assisted and has a black plastic tank inside the porcelain tank, the repairs will be completely different and covered under a different article.

A wobbly toilet will need to be pulled & reset with a new wax ring. The same will also have to be done to fix a toilet that leaks at the base, or has an odor from the wax seal being worn out.

If the toilet fills intermittently, or seems to make noise or flush by itself, the toilet is likely running. If the toilet is over-filling and wont shut off, the fill valve is going bad and will likely have to be replaced.